The burning of fossil fuels in boilers to raise high temperature, high-pressure steam that can be used to power turbo-electric generators produces a problem source of carbon dioxide and other greenhouse gases, e.g. methane, ozone and fluorocarbons. This fossil fuel combustion, especially of coal, needs a technological fix to avoid the emission of carbon dioxide and other greenhouse gases with their attendant undesirable release to the earth's atmosphere resulting in the absorption of solar radiation known as the greenhouse effect. Much of the world depends on coal for power. There have been significant efforts to develop clean coal technologies to greatly reduce the release of acid gases, such as sulfur oxides and nitrogen oxides. However, to date none of these clean coal demonstrations eliminate the emissions of carbon dioxide and other greenhouse gases. Efforts to use pure oxygen in power plants and gasification systems to avoid the diluting effects of nitrogen and to achieve higher efficiency suffers from the unacceptable cost of requiring an air separation plant and the problems of excessive temperatures in oxygen-fed combustion turbo-generators.
There is also widespread effort to increase the efficiency of power plants by utilizing advanced thermodynamic combined cycles, more efficient turbo-generators, improved condensers and cooling towers, and similar systems. A small portion of this effort involves the use of fossil fuel gasification processes, which are highly efficient because they avoid combustion and large combustion product emissions. Finally there is an effort by Westinghouse (Corporate literature, “SureCell®” 1996) and others to combine the use of advanced high temperature turbo-generators and fuel cells to accomplish conversion to electricity at efficiencies of about 70% instead of current conventional combined cycle power plants of about 47%.
The problem with the conventional approach with high temperature fuel cells, which commingles the exhaust from the anode and cathode is that nitrogen and CO2 are mixed, making it very difficult and uneconomic to use the CO2 for sequestration applications (see U.S. Dept. of Energy, National Energy Technology Laboratory, “Solid State Energy Conversion Alliance (SECA) Program,” Pittsburgh, Pa., Aug. 29, 2006 and “7th Annual SECA Workshop and Peer Review,” Philadelphia, Pa., Sep. 12-14, 2006). Under the U.S. Dept. of Energy SECA program the manufacturers have demonstrated that they can isolate the anode and cathode exhaust streams.
Today there is worldwide concern that the atmospheric buildup of carbon dioxide and other greenhouse gases will start to have serious environmental consequences for the earth's tropospheric temperature, global rainfall distribution, water balance, severe weather storms, and similar consequences. Technological solutions are being demanded throughout the world.
The worldwide research establishment, encouraged by government funding from various agencies, continues to be focused on identifying commercially attractive gas separation technologies to remove carbon dioxide from stack gases and also attractive chemistry that will utilize this carbon dioxide as a raw material to manufacture useful products. This has, indeed, been a very large challenge with poor successes as summarized by the review papers; see Michele Aresta, and Eugenio Quaranta, “Carbon Dioxide: A Substitute for Phosgene,” Chem. Tech. pp. 32-40, March 1997, and Bette. Hileman, “Industry Considers CO2 Reduction Methods”, Chem. & Engr. News, pg. 30, Jun. 30, 1997. Trying to scrub the CO2 from stack gases and trying to chemically react the recovered CO2 clearly is not the right path of research because of the technical difficulty and the process expense of reacting carbon dioxide.
The scrubber approach alone is not sufficient for making syngas of high enough quality for fuel cells. Therefore, a great need exists for an improved cleanup system that will produce a syngas of high cleanliness to drive high temperature fuel cells, as well as to destroy a wide range of waste streams generated around the world while to convert this carbonaceous waste into useful hydrogen-rich syngas to drive a fuel cell to produce clean energy.